Fucosyl-GM1 is a sphingolipid monosialoganglioside composed of a ceramide lipid component, which anchors the molecule in the cell membrane, and a carbohydrate component that is exposed at the cell surface. Carbohydrate antigens are the most abundantly expressed antigens on the cell surface of cancers (Feizi T. (1985) Nature 314:53-7). In some tumor types, such as small cell lung cancer (SCLC), initial responses to chemotherapy are impressive, but chemo-refractory relapses rapidly follows. Intervention with novel immunotherapeutics may succeed in overcoming drug resistant relapse (Johnson D H. (1995) Lung Cancer 12 Suppl 3:S71-5). Several carbohydrate antigens, such as gangliosides GD3 and GD2, have been shown to function as effective targets for passive immunotherapy with MAbs (Irie R F and Morton D L. (1986) PNAS 83:8694-8698; Houghton A N et al. (1985) PNAS 82:1242-1246). Ganglioside antigens have also been demonstrated to be effective targets for active immunotherapy with vaccines in clinical trials (Krug L M et al. (2004) Clinical Cancer Research 10:6094-6100; Dickler M N et al. (1999) Clinical Cancer Research 5:2773-2779; Livingston P O et al. (1994). J Clin Oncol. 12:1036-44). Indeed, serum derived from SCLC patients who developed antibody titers to Fucosyl-GM1 following vaccination with KLH conjugated antigen, demonstrated specific binding to tumor cells and tumor specific complement dependant cytotoxicity (CDC). Anti-Fucosyl-GM1 titer associated toxicities were mild and transient and three patients with limited-stage SCLC were relapse-free at 18, 24, and 30 months (Krug et al., supra; Dickler et al., supra).
Fucosyl-GM1 expression has been shown in a high percentage of SCLC cases and unlike other ganglioside antigens, Fucosyl-GM1 has little or no expression in normal tissues (Nilsson et al. (1984) Glycoconjugate J 1:43-9; Krug et al., supra; Brezicka et al. (1989) Cancer Res 49:1300-5; Zhangyi et al. (1997) Int J Cancer 73:42-49; Brezicka et al. (2000) Lung Cancer 28:29-36; Fredman et al. (1986) Biochim Biophys Acta 875: 316-23; Brezicka et al. (1991) APMIS 99:797-802; Nilsson et al. (1986) Cancer Res 46:1403-7). The presence of Fucosyl-GM1 has been demonstrated in culture media from SCLC cell lines, in tumor extracts and serum of nude mouse xenografts and in the serum of SCLC patients with extensive-stage disease (Vangsted et al. (1991) Cancer Res 51:2879-84; Vangsted et al. (1994) Cancer Detect Prev 18:221-9). These reports provide convincing evidence for Fucosyl-GM1 as a highly specific tumor antigen, which may be targeted by an immunotherapeutic.
Accordingly, agents that recognize Fucosyl-GM1, and methods of using such agents, are desired.